Slow-Moving Vehicle

Traffic jams are not, by and large, caused by flaws in road design but by flaws in human nature. While this is bad news for drivers — there’s not much to be done about human nature — it is good news for readers of Tom Vanderbilt’s new book. “Traffic” is not a dry examination of highway engineering; it’s a surprising, enlightening look at the psychology of human beings behind the steering wheels.

An alternate title for the book might be “Idiots.” Vanderbilt, who writes regularly about design and technology, cites a finding that 12.7 percent of the traffic slowdown after a crash has nothing to do with wreckage blocking lanes; it’s caused by gawkers. Rubberneckers attend to the spectacle so avidly that they themselves then get into accidents, slamming into the car in front of them when it brakes to get a better look or dig out a cellphone

to take a picture. (This happens often enough for traffic types to have coined a word for it: “digi-necking.”) Exasperated highway professionals have actually tried erecting anti-rubbernecking screens around the scenes of accidents, but the vehicle toting the screen typically gets caught in the traffic jam it’s meant to prevent.

Moreover, Vanderbilt adds, “there is the interest in the screen itself.” Drivers will slow down to look at anything: “Something as simple as a couch dumped in a roadside ditch can send minor shudders of curiosity through the traffic flow.” “Traffic” is jammed with these delicious you’ve-got-to-be-kidding moments.

Even without home furnishings to distract us, we rarely seem to get anywhere fast at any time of day. One reason, Vanderbilt reports, is that people are driving to do things they once did at home or down the block. “It is not just that American households have more cars,” he writes, “it is that they are finding new places to take them.” They’re going someplace to eat. They’re driving to Whole Foods because they don’t like the produce at their neighborhood supermarket. They’re going out to get coffee. (So much of Starbucks’s revenue now comes from drive-through lanes that the company will put stores across the street from each other, sparing drivers “the agony of having to make a left turn during rush hour.”)

And they’re parking. Or trying to. In a study of one 15-block area near U.C.L.A., cars were logging, on an average day, 3,600 miles in pursuit of a place to park. It’s not only the number of parkers on the roads that slows things down. It’s the way they drive, crawling along, sitting and waiting and engaging in other irritating examples of what one expert calls “parking foreplay.” The answer? Sorry: more expensive street parking to encourage the circling hordes to use pay lots.

Traffic does not yield to simple, appealing solutions. Adding lanes or roads is a short-lived fix. Widen one highway, and drivers from another will defect. Soon that road is worse than it was before. The most effective, least popular solution — aside from the currently effective, unpopular solution of $5-a-gallon gasoline — is congestion pricing: charging extra to use roads during rush hours. For unknown reasons, Americans will accept a surcharge for peak-travel-time hotel rooms and airfares but not for roads.

If it’s any consolation, traffic has always been bad. Vanderbilt begins with a short (I longed for more!) section on the history of traffic congestion. By studying chariot “rutways” and “wear patterns on curbstones,” archaeologists have determined that the citizens of Pompeii had to contend with construction detours and one-way streets. Meanwhile, in ancient Rome, “the chariot traffic grew so intense that Caesar ... declared a daytime ban on carts and chariots, ‘except to transport construction materials for the temples of the gods or for other great public works or to take away demolition materials.’”

I was less surprised by all that than by the existence of so many traffic professionals. Given the seeming anarchy of traffic, there are a surprising variety of experts employed to manage it. Vanderbilt has interviewed them all, from traffic “vision specialists” (who have, of late, taken to making road signs in “incident pink”) to “one of the world’s leading authorities on queues.” (One of!) The author is an impressively energetic researcher, even, at one point, tracking down the person who programs the Hebrew calendar into about 75 signal lights in Los Angeles. This is done to enable Sabbath-observant Jews to cross the street without pushing a button and violating the ban on operating machinery. (In New York it isn’t necessary, as most crossing buttons long ago stopped working.)

Vanderbilt spends much time deconstructing crashes — a problem even before there were cars. “In the New York of 1867,” he writes, “horses were killing an average of four pedestrians a week (a bit higher than today’s rate of traffic fatalities).” Nowadays, the cause of collisions, or one of them, is people believing they’re better drivers than they are. We base our judgment on the number of crashes we’ve been in, rather than on the number of accidents we narrowly avoid, which, if we’re being honest (or we’re being me), happen just about every time we drive. Compounding this vehicular hubris is the fact that most of the driving we do appears to be safer than it is. Driving rarely commands 100 percent of our attention, and so we feel comfortable multitasking: talking on the phone, unfolding a map, taking in the Barca-Lounger on the road’s shoulder. Vanderbilt cites a statistic that nearly 80 percent of crashes involve drivers not paying attention for up to three seconds. Thus the places that seem the most dangerous — narrow roads, hairpin turns — are rarely where people mess up. “Most crashes,” Vanderbilt writes, “happen on dry roads, on clear, sunny days, to sober drivers.” For this reason, roads that could be straight are often constructed with curves — simply to keep drivers on the ball.

This basic truth — feeling safe kills — lies beneath many of the book’s insights. Americans think roundabouts are more dangerous than intersections with traffic lights. Roundabouts require you to adjust your speed, to merge, in short, to pay attention. At an intersection, we simply watch the light. And so we may not notice the red-light runner coming at us or the pedestrian stepping off the curb. A study that followed 24 intersections that had been converted from signals or stop signs to roundabouts showed an almost 90 percent drop in fatal crashes after the change.

For similar reasons, S.U.V.’s are more dangerous than cars. Not just because they’re slower to stop and harder to maneuver, but because — by conferring a sense of safety — they invite careless behavior. “The safer cars get,” Vanderbilt says, “the more risks drivers choose to take.” (S.U.V. drivers are more likely to not bother with their seat belts, to talk on cellphones, and to not wear seat belts while talking on cellphones.) So it goes for much of the driving universe. More people are killed while crossing in crosswalks than while jaywalking. Drivers pass bicyclists more closely on a road with bike lanes than on one without.

My solution to the nation’s vehicular woes would be to make this good book required reading for anyone applying for a driver’s license. Though you could then be sure that some percentage of car crashes in America would be caused by people trying to skim “Traffic” while stuck in a bottleneck on their way to the D.M.V.

TRAFFIC

Why We Drive the Way We Do (And What It Says About Us).

By Tom Vanderbilt.

402 pp. Alfred A. Knopf. $24.95.

Mary Roach’s most recent book is “Bonk: The Curious Coupling of Science and Sex.”

A version of this review appears in print on , on page BR1 of the Sunday Book Review with the headline: Slow-Moving Vehicle. Today's Paper|Subscribe